1. Technical Field
The embodiments described herein relate to a periodic signal generating circuit and, more particularly, to a refresh periodic signal generating circuit.
2. Related Art
Volatile memory devices generally require periodic refresh operations to be periodically carried out to assure the integrity of the stored data. These types of volatile memory devices include semiconductor integrated circuits, such as a DRAM (Dynamic Random Access Memory). The refresh period can be frequently changed in accordance to PVT (Process, Voltage, and Temperature) variation needs. For example, generally high temperature conditions require relatively quick refresh periods and low temperature conditions can be extend the refresh periods.
Generally when the refresh period are extended, it becomes more and more difficult to assure that the integrity of the data is valid. However when the refresh period are shorten, then large amounts of refresh current are needed and thus power may be used inefficiently. It is usually deemed necessary to simply generate refresh signals within a constant cycle period to assure stable operations even if there are a temperature variations in the working semiconductor integrated circuit.